Github user chenghao-intel commented on the pull request:
https://github.com/apache/spark/pull/1567#issuecomment-60343575
@rxin @marmbrus , I've uploaded an draft design doc in jira.
https://issues.apache.org/jira/secure/attachment/12676811/grouping_set.pdf,
sorry it maybe not cover every detail, let me know if you have any confusion.
@marmbrus
>The creation of bit vectors seems like a very implementation focused
physical concern. I'm curious if this could be restricted to the actual
physical operator.
Yeah, It's very reasonable, I was thinking of this either.
However, the bit vectors stuff don't rely on physical execution engine, and
it's slightly different with the Aggregate, which has the optimization of
mapside aggregation for spark execution.
Besides, the attribute reference pass down to the parent logical operator
need to be correctly set in logical plan analyzing.
Anyway, I will consider your suggestion, after all, we should keep the
Logical Plan for "describing what to do", not "how to do".
>Adding a new type of attribute reference for virtual columns might be a
lot of overhead. Is this really necessary?
A concrete `VirtualColumn` instance is very helpful in attribute
referencing, and pattern matching, probably better than a name convention.
Sorry, maybe I didn't understand your mean, we can discuss that in the code
review.
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